Chapter 6Skin and the Integumentary SystemYou will be able to: ACOS 5 Identify anatomical structures and functions of the integumentary system Identify accessory organs Recognize diseases and disorders of the integumentary system (examples: decubitus ulcer, melanoma, psoriasis)

Integumentary system: skin and its accessory organIncludes two distinct layersepidermisouter layer composed of stratified squamous epitheliumdermisinner layerthicker than the epidermiscontains dense connective tissue consisting of collagenous and elastic fibers, epithelial tissue, smooth muscle tissue, nervous tissue, and blood

A basement membrane anchors the epidermis to the dermis and separates these two skin layers.Beneath the dermis are masses of loose connective tissue and adipose tissues that bind the skin to the underlying organs called the subcutaneous layer (or hypodermis). This is beneath the skin and not a true layer of skin.It also serves as a shock absorber or insulator.

EpidermisComposed of five zones or stratastratum basale deepest cell layerclose to the dermis and is nourished by dermal blood vesselsconstantly undergoing cell divisionstratum spinosumstratum granulosum

KeratinizationThe older cells being pushed toward the surface harden in a process called keratinization.The cytoplasm fills with strands of tough, fibrous, waterproof keratin protein.As a result, many layers of tough, tightly packed cells accumulate in the outermost areas, stratum lucidum and stratum corneum.

stratum lucidumfound only on hands and soles of feetstratum corneumoutermost layer20 to 30 cell layers thickdead cells that form this layer eventually are shed

Melaninpigment that ranges in color from yellow to brown to blackproduced by special cells called melanocytes found mostly in the stratum basaleFreckles and moles are concentrated spots of melanin.How do we tan?What happens when we receive excessive exposure to the sun?

Skin ColorDifferences in skin color result from differences in the amount of melanin that melanocytes produce and in the distribution and size of the pigment granules.Skin color is mostly genetically determinedif genes instruct melanocytes to produce abundant melanin, then the skin is dark.

William Bryant Staffordwith jaundice (sun tanning)

Dermisstrong, stretchy envelope that helps hold the body together (your hide) dense, fibrous connective tissue of the dermis consists of two major regions1. papillary layerupper region2. reticular layerdeepest skin layer

1. Papillary Layerdermal papillaefingerlike projections from the superior surface of the papillary layer that cause it to be uneven; contain capillary loops, pain receptors or touch receptors

Meissners corpusclestouch receptors

Papillary patterns are genetically determined. Fingerprints are unique, identifying films of sweat caused by the ridges of the fingertips.

2. Reticular Layercontains blood vessels, sweat and oil glands, and deep pressure receptors called Pacinian corpusclescontains many phagocytes that act to prevent bacteria that have gotten through the epidermis from penetrating any deeper into the bodycontains collagen and elastic fibersabundantly supplied with blood vessels that play a role in maintaining body temperatureWhat are decubitus ulcers? Blue Box page 116

Skin Section

Subcutaneous Layer (Hypodermis)consists of loose connective tissue and adipose tissueno sharp boundary between the dermis and subcutaneous layerprovides insulation, helping to conserve body heat and impeding the entrance of heat from the outside

Accessory Organs of the SkinNails scalelike modification of the epidermishas a free edge, a body (visible attached portion), and a root (embedded in the skin)nail foldsskin folds that overlap the borders of the nailscuticlethick proximal nail foldnail bedstratum basale that extends beneath the nailnail matrixthickened proximal area responsible for nail growthlunularegion over the thickened nail matrix that appears as a white crescent

Accessory Organs of the SkinHairmillions scattered all over the bodyserves only a few functionsguarding the head from bumps, shielding the eyes, and helping to keep foreign objects out of the respiratory tractproduced by a hair follicle

parts of a hair:1. medullacentral core2. cortexbulky layer that surrounds the core3. cuticleoutermost layer that encloses the cortex; formed by a single layer of cells that overlap one another

Hair Folliclerootpart of the hair enclosed in the follicleshaftpart of the hair projecting from the surface of the scalp or skinhair bulb matrixgrowth zone at the end of the follicle where hair is formed by the division of stratum basale epithelial cellsarrector pilismall bands of smooth muscle cells that connect each side of the hair follicle to the dermal tissue

Sebaceous (Oil) Glandsfound all over the skin expect palms of the hands and soles of the feetducts usually empty into a hair follicle but some open directly to skin surfacesebummixture of oily substances and fragmented cells that acts as a lubricant to keep skin soft and moist and prevent hair from becoming too brittlesebum contains chemicals that kill bacteria so it acts as a protectant

Sudoriferous (Sweat) Glandswidely distributed in the skinmore than 2.5 million per persontwo types:A. eccrine glandsfar more numerous and found all over the body; produce sweat when hotB. apocrine sweat glandslargely confined to the axillary and genital areas of the body; activated at puberty

Regulation of Body Temperaturepage 120Write and answer the following questions.What is the normal temperature of deep body parts?What body part plays a key role in regulating body temperature?How does the body react when the body temperature rises?How does the body react when the body temperature drops?Where does 80% of the bodys heat escape?

Healing of Woundspages 120-121inflammation: when a wound becomes red and swollen due to fluids entering the damaged tissuesscab: blood clot and dried tissue fluids that cover and protect underlying, damaged tissuescar: connective tissue that forms on the surface of the skin of extensive woundsgranulations: small, rounded masses consisting of a new branch of a blood vessel and a cluster of collagen-secreting fibroblasts

Before 1st bulletRead 1st two paragraphs on page 113.

After endA burn or friction (like the rubbing of a poorly fitting shoe) may cause the two layers to separate, which results in a blister.

Pass out handout of Table 4.1 and go over the functions of the skin.Point out the layers on the picture.

Quick FactIf the skin of a 150-pound person were spread out flat, it would cover approximately 20 square feet.After 3rd starMillions of new cells are produced daily. Cells are being pushed upward to become other cell layers. As they move closer the surface, they become flatter, and the poorer the nutrient supply becomes, so the die.After 1st starSo in most places, there are only four strata of skin.After 3rd staraccounts for about three-quarters of the epidermal thickness

After 4th starRead 2nd paragraph on page 114.

The common saying Beauty is only skin deep is especially interesting in light of the fact that nearly everything we see when we look at someone is dead! The stratum corneum rubs and flakes off slowly and steadily and is replaced by the division of the deeper stratum basale cells. SO, we have a totally new epidermis every 25 to 45 days.After 4th bulletWhen skin is exposed to sunlight, melanocytes are stimulated to produce more melanin?

After 5th bulletDespite melanins protective effects, excessive sun exposure eventually damages the skin. It causes the elastic fibers to clump, leading to leathery skin. It also depresses the immune system. Overexposure can also alter the DNA of skin cells and can lead to skin cancer. Black people seldom have skin cancer, attesting to melanins amazing effectiveness as a natural sunscreen.Before 1st bulletSkin color is due largely to melanin. All people have about the same number of melanocytes in their skin.

After last bulletRead 2nd paragraph on page 116.After 1st bulletWhen you purchase leather goods (like bags or belts), you are buying the treated dermis of animals.

After 2nd bulletranges in thickness-thick on palms of hands and thin on eyelidsAfter 1st bulletthe capillary loops provide nutrients to the epidermis; pain receptors are just free nerve endings

After 3rd bulletGenes determine the fingerprint patterns, but the patterns can change slightly as a fetus moves and presses the forming ridges against the uterine wall which is why the fingerprints of identical twins are usually not exactly alike.After 3rd bulletelastic fibers give the skin its elasticity when were youngas we age, the number of fibers decreases as well as the amount of adipose tissue and our skin becomes less elastic beginning to sag and wrinkle.

After last bulletRead 1st blue box on page 116.Point out dermal papillae, Meissners corpuscles, Pacinian corpuscles, the papillary and reticular layers.After 3rd bulletdue to all the adipose tissue

Have students complete the Check Your Recall questions on pages 114 and 116.After 1st bulletcorresponds to the hoof or claws of animals

The thumbnail grows the slowest; the middle nail grows the fastest.

At endNails are transparent and nearly colorless. They look pink because of the rich blood supply in the underlying dermis.After 2nd bulletServed early humans (and animals now) by providing insulation in cold weather

After 3rd bulletoverlap like shingles on a roofAfter 4th bulletThis muscle is positioned so that a short hair within the follicle stands on end when the muscle contracts. If a person is emotionally upset or very cold, nerve impulses may stimulate the arrector pili muscles to contract, causing goose bumps.

Read about hair color in 2nd paragraph on page 118.Read blue box in second column of page 118 about acne.After 1st bulletEach gland consists of a tiny tube that originates as a ball-shaped coil in the deeper dermis or superficial subcutaneous layer.

Sweat is mostly water, but also contains small quantities of salt and wastes, such as urea and uric acid.

After AThese glands are common on the forehead, neck, and back where they produce profuse sweat on hot days or during intense physical activity.

After BThese glands become active at puberty. The secretion contains fatty acids and proteins, as well as substances present in eccrine secretion; may have a milky or yellowish color. The secretion is usually odorless but can take on a musky, unpleasant odor when bacteria is on the skin.98.6 F (37 C)SkinRead 3rd and 4th paragraph.Read 5th paragraph.Head (which is why hats are essential in the winter)After 1st bulletBlood vessels dilate forcing fluids to leave and enter tissues. Inflamed skin may become red, warm, swollen, and painful to the touch. The dilated blood vessels, however, provide the tissues with more nutrients and oxygen which aids in healing. Read 2nd paragraph.

After 2nd bulletread 1st paragraph on page 121.

After 4th bulletRead last paragraph on page 121.